Engine start and shutdown system

ABSTRACT

A control circuit for a diesel engine provides for simplified staring and for manually initiated shutdown and also provides for automatic shutdown in the event that any of various warning devices detect an undesirable condition such as insufficient oil pressure, excess engine temperature or overspeed. A single manually operated control switch has a Start position for energizing the starter motor, an Off position for energizing a solenoid at the engine governor to shut off the fuel supply, and a Run position at which a solid state shutdown circuit energizes the governor solenoid if gated by a warning signal from any of the indicator devices. The system may use the sensors of the normal visual warning gauges and provides for starting of the engine by manipulating only a single element at the control switch.

United States Patent Wagner [451 Apr. 25, 1972 s41 ENGINE START AND SHUTDOWN 3,154,689 10/1964 Bubbenmoyer ..290/3s SYSTEM Primary Examiner-Herman J. Hohauser [72] Inventor Harold Wagner Peona Att0rneyFryer, Tjensvold, Feix, Phillips & Lempio [73] Assignee: Caterpillar Tractor Co., Peoria, Ill. 22 Filed: May 25, 1970 [57] ABSTRACT A control circuit for a diesel engine provides for simplified [21] Appl' 39994 staring and for manually initiated shutdown and also provides for automatic shutdown in the event that any of various warn- [52] U.S.Cl. ..307/9, 180/103 X, 340/52 F, ing devices detect an undesirable condition such as insuffi- 317/9 B cient oil pressure, excess engine temperature or overspeed. A [51] Int. Cl. ..H02j 1/00 si le anually perated control switch has a Start position Field of Search 103 317/9 B; for energizing the starter motor. an Off position for energizing 307/9, 10 R, 10 BP, 10 AT; 290/7, 1; 340/52 X, 53, a solenoid at the engine governor to shut off the fuel supply, 52 F; zgo/DIG' 40 and a Run position at which a solid state shutdown circuit energizes the governor solenoid if gated by a warning signal [56] References cued from any of the indicator devices. The system may use the sen- UNITED STATES ATENTS sors of the normal visual warning gauges and provides for starting of theengme by manipulating only a single element at 2,992,303 7/1961 Murphy ..317/9 B the control i h; 3,517,382 6/1970 Stein et a]. 1,854,571v 4/1932 Albertson ..317/9 B 7 Claims, 1 Drawing Figure 37' 32 4; 45 STOP 33 GLOW E L3 39 k I 7 r38 PLUGS 1. I 22 A 1 (l 39' i I T RT i 42 I 1';- SO LENOID 1 1:" I

,: I I -1 r ENGlNE WATER OIL PRESSURE TEMP.

OTHER SENSORS ENGINE START AND SHUTDOWN SYSTEM BACKGROUND OF THE INVENTION This invention relates to internal combustion engines and more particularly to control circuits for initiating starting and stopping of an engine and having means for automatically stopping the engine in the event certain undesirable conditions develop.

Various conditions can develop in an operating engine which might cause damage if the engine is not shutdown promptly and it is customary to provide indicator devices for alerting the operator if these conditions appear. Engines are, for example, customarily provided with an oil pressure gauge and water temperature gauge and in some cases with other indicators as well.

Where these devices are purely indicators, avoidance of engine damage depends on the operators alertness and willingness to take such corrective action as is needed. Greater reliability is obtained if the control system acts automatically to shut down the engine when any of the several unsafe conditions develop. In certain engine usages, such as in highway vehicles, automatic shutdown may not be desirable in that the traffic hazard created by an unexpected stoppage of a vehicle can be more serious than the risk of engine damage. This is not necessarily true of many other engine applications such as in off-highway vehicles used for earthworking purposes or in stationary engines. In many of these engines, it has been the practice to provide for automatic shutdown.

An engine having an electrical ignition system is readily shut down by opening the ignition circuit. Shutdown of certain other forms of engine, such as those of the diesel variety, is

more complicated as it is necessary to apply a sizable force to a fuel supply control member which is usually located in the engine governor. This is generally accomplished with a solenoid which requires a sizable current. Because of the current requirements of the solenoid, it has heretofore been necessary to use engine monitoring devices which are complicated by adaptations for handling high current or else to provide duplicate sensors which are separate from the operators warning devices.

Still further factors have contributed to an undesirable degree of complication in automatic shutdown systems. Starting of the engine, for example, required manipulation of controls additional to the starter switch. The reason for this is that certain of the conditions which may initiate automatic shutdown are conditions which are inherently present at'the time the operator attempts to start the engine. Oil pressure, for example, is absent when starting of the engine is first initiated and if the control system is designed to shut down the engine in the presence of low oil pressure, then the system must be rendered temporarily inactive during the start-up period. This has heretofore necessitated that the operator manipulate an additional control element, such as a relay latch, either prior to or concurrent with operation of the starter switch itself. In some of these systems, the automatic shutdown may remain inactive after the engine starts, if oil pressure does not build up to reactivate the system. Thus operation with insufficient oil pressure is possible.

Still a further disadvantage of conventional systems is that temporary fluctuations in certain monitored engine conditions can cause erratic operation as the system alternately initiatesa shutdown and then permits re-application of fuel before the engine has completely stopped.

SUMMARY OF THE INVENTION This invention is an engine starting and stopping circuit which also provides for automatic shutdown in the event of certain undesirable conditions and which is relatively free from the operating complications, structural complexities, and other undesirable factors discussed aboverln a preferred form, the operators control switch has a Start position and a Stop position and is spring returned to a Run position at which the automatic shutdown system is operative, the automatic system being disabled at the Start position of the control switch. Upon detection of an undesirable condition, the operators warning indicator devices provide a low current gating signal to solid state circuitry which applies a relatively high current to the engine governor solenoid to cut off fuel supply, the circuit being arranged to hold the engine in a shutdown condition until the operators control switch is reoperated.

Accordingly, it is an object of this invention to provide a less complex and more reliable means for safeguarding an engine against damage from continued operation in the presence of adverse operating conditions such as low oil pressure, excess temperature and the like.

It is another object of the invention to provide an engine control circuit providing for starting, manually initiated shutdown and automatic shutdown wherein the operators manipulations at start-up are simplified and wherein moving parts are minimized and wherein low power electrical sensor devices may beutilized.

The invention, together with further objects and advantages thereof, will best be understood by reference to the following description of a preferred embodiment taken in conjunction with the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING The accompanying drawing depicts an engine control system in accordance with the invention including structural details of certain electro-mechanical elements, with certain other components being shown in schematic and diagrammatic form.

DESCRIPTION OF A PREFERRED EMBODIMENT Referring now to the drawing, internal combustion engines to which the present invention is applicable may be of conventional construction and accordingly an engine 11 is shown only in block form to avoid unnecessary complication of the drawing. Virtually any conventional internal combustion engine 11 includes some element which may be manipulated to shutdown the engine and in the present example, wherein the engine 11 is of the diesel variety, this element is a shaft 12 in a governor 13 which may be shifted in one direction to increase the rate of fuel supply to the engine and which decreases fuel input, and eventually shuts off the fuel supply, if shifted in the opposite direction. Engine governor 13 may be of conventional construction and accordingly will not be described in detail herein except for certain elements which coact directly with the engine control circuit. In particular, a governor 13 for a diesel engine 11 is frequently provided with a solenoid coil l4 having terminals 16 and a movable armature 17 which is shifted against the action of a spring 18 by the application of an electrical current to the terminals. Armature 17 is arranged to operate a lever 19, secured to a pivot 21, which engages a flange 22 on governor shaft 12 to draw the shaft 12 towards the fuel shut-off position when the solenoid coil 14 is energized.

In the case of an engine of the type having an electrical fuel ignition system, solenoid 14 may be the driver, coil of a relay for opening the ignition circuit upon energization of the solenoid. In gas turbine engines, fuel supply is also controlled by a movable element similar to shaft 12.

To enable the operator to start and stop the engine 11 a manually operated control switch 23 is provided, the switch being of a specialized construction in the present invention to provide for a Stop setting in addition to the Heat, Start" and Run settings which are found in a control switch for a diesel engine. The switch 23 in this example has a fixed back member 24 with a circular cavity in the forward face into which a conforming rotatable switch cylinder 26 is received.

A front member 27 defining an interior chamber 28 is secured to back member 24. To enable the operator to rotate cylinder 26 a shaft 29 extends axially therefrom through front member 27 and a suitable knob 31 is fastened to the forward end for manipulation by the operator. Knob 31 may be key operated in the conventional manner if desired. An electrically conductive wiper element 32 is secured to the forward face of switch cylinder 26 and extends radially therefrom, the outer end 33 of the wiper element having the shape of a sector of a circle. A spiral coil spring 34 has an inner end engaging shaft 29 and an outer end engaging a post 36 fixed to back member 24 to provide a spring centering force which urges the switch cylinder 26 to an angular orientation defining a Run position of the switch at which wiper end 33 bridges two spaced apart contacts 37 and 38 on the forward face of back member 24 and which are equidistant from the axis of shaft 29.

Contact 37 is electrically connected with a run terminal 37 mounted in back member 24 and in this example is situated directly above shaft 29 at the center of the top portion of the forward surface of member 24. Contact 38 is'a dead contact which has no electrical function but serves to provide support for the wiper element 32 in the described position and also in a Heat position to be hereinafter described.

Counter clockwise motion of the control knob 31 from the above described Run position turns wiper element 32 to a Stop position at which wiper end 33 bridges the contact 37 and another contact 39 also mounted in the forward face of back member 24. A first amount of clockwise rotation of the knob 31 from the Run position moves the wiper end 33 to bridge the dead contact 38 and another contact 41 which is electrically connected to a terminal 41 mounted in back member 24 to define a Heat setting of the control switch 23. Further clockwise movement of knob 31 establishes a Start position by turning the wiper end 33 to bridge contact 41 and still another contact 42 electrically connected to a start terminal 42' in back member 24.

To provide positive battery voltage to wiper element 32 at the above described Heat position and Start position of the control switch 23, an arcuate contact 43 is mounted in the forward face of back member 24 between contacts 41 and 42 and switch cylinder 26 in a position to be contacted by the wiper element at either of the above described settings. Arcuate contact 43 is electrically connected with a first B+ terminal 43 in back plate 24 which is connected with the positive terminal of the vehicle battery 44, the negative side of the battery being grounded. Thus, when the control switch 23 is operated to the Heat position, positive battery voltage is transmitted from contacts 43' and 43 to contact 41 and terminal 41'. Terminal 41 is connected to the glow plugs 45 of diesel engine 11 to provide for preheating of the engine prior to starting. When the control switch 23 is shifted to the Start position, battery voltage is supplied to contact 42 as well as contact 41. Contact 42, through terminal post 42, is connected to the starter motor solenoid 46. Thus at the Start position of the control switch, the starter motor solenoid 46 is energized to start the engine 11 while the glow plugs 45 continue to be energized.

Positive battery voltage is also supplied to wiper 32 at both the Run and Stop positions of the control switch 23 and for this purpose an additional arcuate contact 47 is situated at the forward face of back member 24 between switch cylinder 26 and contacts 37 and 39. Arcuate contact 47 is electrically connected with a terminal 47 in back member 24 which is in turn connected to the positive side of vehicle battery 44 through a fuel pressure switch 48 which is normally closed during engine operation as will hereinafter be discussed in more detail.

The Stop position of control switch 23 provides for a manually initiated shutdown of the engine 11 as contact 39 is connected to a terminal 39' in back member 24 that is in turn connected to one of the governor solenoid terminals 16, the other solenoid terminal being grounded and a diode 49 being connected across the two terminals 16 to suppress transient voltage spikes. At the Stop position, positive battery voltage from terminal 47 is conducted to contact 39 by wiper 32 and thus is supplied to the solenoid coil 14 which operates to shift governor shaft 12 and cut off the supply of fuel to engine 11. The fuel switch 48 functions to avoid continuous energization of solenoid coil 14 after the engine shutdown has been accomplished. Such fuel switch 48 may be of the known form which is closed by the presence of a predetermined level of fluid pressure in the engine 11 and which opens in the absence of such pressure. Accordingly, when engine 11 has shut down, fuel switch 48 opens to remove positive battery voltage from the solenoid coil 14.

When the operator releases knob 31 following starting of engine 1], spring 34 returns the control switch 23 to the Run position at which positive battery voltage from terminal 47' is transmitted to terminal 37 by the wiper 32 to energize an automatic shutdown circuit 50. Detent means 51 are provided to assist in holding the switch at the Run setting and also at the Off setting against the action of spring 34. The detent means 51 may comprise a compression spring 52 situated in a bore 53 in back member 24, the bore being aligned along a radius of switch cylinder 26. A ball 54 is disposed in bore 53 and is urged against the adjacent surface of switch cylinder 26 by spring 52, the switch cylinder being provided with notches 55 and 55 into which a portion of the ball is forced when the switch plate is rotated to the Run position or the Off position respectively. The spring loaded ball 54 thus exerts a force tending to resist switch cylinder rotation at either of these positions.

Considering now the circuit 50 for initiating an automatic shutdown of engine 11 in the event that any of various undesirable operating conditions develop, the B+ terminal 16 of governor solenoid 14 is connected to control switch terminal 37 through an SCR (silicon controlled rectifier) 56 which is non-conductive until such time as a gating signal is applied. Accordingly, solenoid coil 14 normally remains unenergized when control switch 23 is at the Run position although terminal 37 of the control switch is energized at that position. Circuit 50 initiates a gating signal to produce conduction through SCR 56 upon the occurrence of any one of several ad verse engine operating conditions. Circuit 50 may include a PUT (programmable unijunction transistor) 64 having cathode side coupled to the gate of SCR 56 and coupled to ground through a resistor 66. The PUT 64 becomes conductive when a predetermined voltage differential exists between base inputs 67 and 67, the first input 67 being a reference base and being connected to 8+ voltage terminal 37 of the operators control switch 23 through a diode 68 and resistor 69. Base input 67"of PUT 64 connects with a ground signal conductor 71 through a resistor 72 and an additional resistor 73 is connected between resistors 69 and 72. To eliminate the effects of transient voltage spikes, a capacitor 74 connects the junction between resistors 69 and 73 with ground.

The action of the gating signal circuit 50 is thus determined by the condition of conductor 71. In particular, if the conductor 71 is not grounded, then there is not a significant voltage difference between PUT base inputs 67 and 67 and no gating signal is delivered to SCR 56 to energize solenoid l4 and initiate an engine shutdown. lf conductor 71 is grounded, PUT 64 conducts and the gating signal developed across resistor 66 triggers SCR 56 into conduction to energize solenoid l4 and shut down the engine 11.

Automatic shutdown is provided for by coupling any desired number of engine indicator devices 76 between conductor 71 and ground. In this example, the indicator devices 76 include an oil pressure gauge 77, water temperature gauge 78, an engine overspeed indicator 79 each being of the form having internal switch means in addition to visible indicators. Indicator devices 76 are shown schematically in the drawing inasmuch as suitable detailed construction for such devices is known to the art. Oil pressure indicators 77, for example, includes switch contacts 77 which close to ground conductor 71, when engine oil pressure is below a predetermined minimum desirable level. Water temperature indicator 78 includes switch contacts 78' which close when engine temperature exceeds a predetermined maximum safe level. Similarly, engine overspeed indicator 79 includes switch contacts 79 which close in the presence of potentially destructive engine overspeed, to ground conductor 71. Any additional desired number of engine condition sensor devices may be similarly connected between conductor 71 and ground.

Thus while operators control switch 23 is at the Run position closing of the internal contacts of any one of the indicator devices 76 grounds conductor 71 causing PUT 64 to deliver a gating signal to SCR 56. SCR 56 then applies B+ voltage to solenoid 14 to shut down engine 11 as previously described. It should be noted that the system is free of the disadvantages of prior shutdown systems as hereinbefore discussed. In particular, manual operation of the control switch 23 to the Heat or Start position removes B+ voltage from SCR 56 rendering the automatic shutdown system inactive at that time and thereby avoiding the need to manipulate a separate latch or the like for this purpose. This is necessary in prior systems in that oil pressure indicator 77 is normally closed at such time and would cause the automatic system to prevent starting of the engine. Further, it is not necessary that the indicator devices 76 carry the heavy current necessary to operate solenoid 14. The indicator devices need only carry a very small current sufficient to generate a gating signal for SCR 56 and may therefore be of a light and economical and long lasting construction. Still further, an undesirable engine operating condition cannot cause repeated alteration between engine operation and partial automatic shutdown. Once SCR 56 becomes conductive, solenoid 14 remains energized until fuel switch 48 opens, notwithstanding intermittent closing or opening of any of the indicator devices 76 in the interval. Further, the engine 11 cannot be operated in the absence of adequate oil pressure as in prior systems wherein an oil indicator device such as device 77 is latched open and may fail to unlatch if oil pressure does not build up after starting.

What is claimed is:

1. In a system for starting and shutting down an engine which has a starter motor and an electrically operated shutdown means for shifting an engine shutdown control, the combination comprising:

an electrical power source,

a manually operated engine control switch having a manually movable control member movable to a Start position at which said control switch actuates means for causing said power source to be coupled to said starter motor, the same control member being further movable to a Run position at which said power source is coupled to output terminal means at said control switch, said output terminal means being decoupled from said power source when said control member is at said Start position,

a circuit element of the form having a non-conducting state and having a conducting state which is initiated by an electrical gating signal, said circuit element being coupled between said output terminal means of said control switch and said shutdown means of said engine,

at least one sensor device having switch members which change state upon occurrence of an undesired engine operating condition, and

a gating signal generating circuit connected between said switch members of said sensor device and said circuit element for gating said circuit element into conduction upon a change of state of said switch members of said sensor device while said control switch is at said Run position thereof.

2. The combination defined in claim 1 wherein said switch members of said sensor device are in condition to activate said gating signal generating circuit when said engine is shut down, said disconnection of the electrical power source from said output terminal of said switch means at said Start position of said control switch preventing said sensor device from initiating a gating signal to shut down said engine while said control switch is at said Start position.

3. The combination defined in claim 2 wherein said sensor device is an engine oil pressure indicator.

4. The combination defined in claim 1 wherein said circuit element is an S CR and wherein said gating signal generating clrcult is comprised of a PUT having an output coupled to the gating signal input of said SCR and having a first base input coupled to said electrical power source through said control switch when said control switch is at said Run position and having a second base input coupled to the opposite terminal of said power source through said sensor device switch members.

5. The combination defined in claim 1 wherein said control switch has spring means urging said control switch towards said Run position thereof.

6. The combination defined in claim 1 wherein said manually movable control member of said control switch is movable to a Stop position for manually initiating shutdown of said engine by energizing said shutdown means independently of said gating signal generating circuit.

7. The combination defined in claim 6 wherein said control switch has detent means for holding said movable control member at said Run position thereof and at said Stop position thereof, said control member being spring returned towards said Run position from said Start position. 

1. In a system for starting and shutting down an engine which has a starter motor and an electrically operated shutdown means for shifting an engine shutdown control, the combination comprising: an electrical power source, a manually operated engine control switch having a manually movable control member movable to a Start position at which said control switch actuates means for causing said power source to be coupled to said starter motor, the same control member being further movable to a Run position at which said power source is coupled to output terminal means at said control switch, said output terminal means being decoupled from said power source when said control member is at said Start position, a circuit element of the form having a non-conducting state and having a conducting state which is initiated by an electrical gating signal, said circuit element being coupled between said output terminal means of said control switch and said shutdown means of said engine, at least one sensor device having switch members which change state upon occurrence of an undesired engine operating condition, and a gating signal generating circuit connected between said switch members of said sensor device and said circuit element for gating said circuit element into conduction upon a change of state of said switch members of said sensor device while said control switch is at said Run position thereof.
 2. The combination defined in claim 1 wherein said switch members of said sensor device are in condition to activate said gating signal generating circuit when said engine is shut down, said disconnection of the electrical power source from said output terminal of said switch means at said Start position of said control switch preventing said sensor device from initiating a gating signal to shut down said engine while said control switch is at said Start position.
 3. The combination defined in claim 2 wherein said sensor device is an engine oil pressure indicator.
 4. The combination defined in claim 1 wherein said circuit element is an SCR and wherein said gating signal generating circuit is comprised of a PUT having an output coupled to the gating signal input of said SCR and having a first base input coupled to said electrical power source through said control switch when said control switch is at said Run position and having a second base input coupled to the opposite terminal of said power source through said sensor device switch members.
 5. The combination defined in claim 1 wherein said control switch has spring means urging said control switch towards said Run position thereof.
 6. The combination defined in claim 1 wherein said manually movable control member of said control switch is movable to a Stop position for manually initiating shutdown of said engine by energizing said shutdown means independently of said gating signal generating circuit.
 7. The combination defined in claim 6 wherein said control switch has detent means for holding said movable control member at said Run position thereof and at said Stop position thereof, said control member being spring returned towards said Run position from said Start position. 